Electro-hydraulic pulse motor

ABSTRACT

The disclosure relates to an improved electro-hydraulic pulse motor having an arrangement wherein a novel tubular member is disposed in the chamber of the hydraulic motor part so that a drain opening provided in the chamber for returning the hydraulic fluid which has leaked out of the hydraulic motor part, is displaced in the direction of the output shaft of the hydraulic motor part and as a result of this, hydraulic fluid is always reserved in the chamber to enable lubrication of the moving elements of the hydraulic motor part, even if the electrohydraulic pulse motor is used in the vertical position with the shaft vertically upward.

United States Patent 91 Inaba et al.

[ Sept. 25, 1973 ELECTRO-HYDRAULIC PULSE MOTOR [22] Filed: Dec. 13, 1971 [21] Appl. No.: 207,163

3,361,077 1/1968 Freeman 417/269 3,662,858 5/1972 Peterson 184/103 R 3,623,402 11/1971 Kubilos 91/499 Primary ExaminerWilliam L. Freeh Assistant ExaminerGregory La Pointe Att0rneyAl1an Ratner et al.

[57] ABSTRACT The disclosure relates to an improved electro-hydraulic pulse motor having an arrangement wherein a novel tubular member is disposed in the chamber of the hydraulic motor part so that a drain opening provided in the chamber for returning the hydraulic fluid which has leaked out of the hydraulic motor part, is displaced in the direction of the output shaft of the hydraulic motor part and as a result of this, hydraulic fluid is always reserved in the chamber to enable lubrication of the moving elements of the hydraulic motor part, even if the electro-hydraulic pulse motor is used in the vertical position with the shaft vertically upward.

1 Claim, 1 Drawing Figure ELECTRO-HYDRAULIC PULSE MOTOR DISCLOSURE OF THE INVENTION The present invention relates to an improvement of an electro-hydraulic pulse motor and more particularly relates to an improved internal structure of the hydraulic motor part of an electro-hydraulic pulse motor.

The electro-hydraulic pulse motor has a conventional arrangement in which principal the parts thereof consisting of an electric pulse motor, a rotary pilot valve and an axial piston hydraulic motor, are operatively coupled to each other by a reduction gear and a screwnut coupling having feedback operation and forming a feedback loop in a hydraulic circuit of the electrohydraulic pulse motor.

The above-mentioned conventional electrohydraulic pulse motor works on an operational principle such as disclosed below.

A predetermined amount of rotation of the electric pulse motor shaft in response to an electric pulse input is transmitted to the valve spool of the rotary pilot valve part by means of a reduction gear so as to cause rotation of the spool. The rotation of the spool is transformed into an axial displacement of the valve spool by the above-mentioned screwnut coupling and the axial displacement of the spool opens an oil supply port provided for the rotary pilot valve part so as to introduce hydraulic fluid from the fluid power source actuating the hydraulic motor part to provide an amplified rotational output on the output shaft of the hydraulic motor part, the output being used for driving a machine on the one hand. On the other hand the output rotation of the hydraulic motor part, restores the spool of the rotary pilot valve part again by means of the screw-nut coupling.

In accordance with the above-mentioned principle, when successive pulse inputs are impressed upon the electric pulse motor part, the input of the hydraulic motor part is caused to rotate successively in accordance with the above-mentioned successive pulses and must provide continuous rotational output therefrom which might reach as high as a few thousand revolutions per minute. Therefore, moving elements provided for the hydraulic motor part such as bearings and reciprocal pistons, must always be kept in a lubricated state to prevent seizing up as well as to provide smooth movements of the elements.

The electro-hydraulic pulse motor is often employed e.g. as a drive motor for a numerically controlled machine tool to provide a vertical feed motion to the machine tool, and in this case, the electro-hydraulic pulse motor must be mounted on the machine tool in a vertical position, that is, the output shaft thereof directs upwardly.

However, in the conventional interior structure of the electro-hydraulic motor in the vertical position, hydraulic fluid leaking out of the hydraulic motor part immediately returns via the. return port of the hydraulic line arranged in the electro-hydraulic pulse motor.

Therefore, the hydraulic fluid is not reserved within a chamber of the hydraulic motor part and this fact results in a lack of lubrication oil in the above-mentioned moving elements.

It is an object of the present invention to provide an electro-hydraulic pulse motor having an improved interior structure thereof whereby a constant lubrication of the moving elements of the hydraulic motor part is achieved independently of any mounting position of the electro-hydraulic pulse motor.

The present invention will be more apparent from the ensuing description with reference to the accompanying drawing wherein:

The FIGURE shows a sectional view of an electrohydraulic pulse motor according to the present invention.

In the FIGURE, an electric pulse motor part I is shown coupled to a rotary type four way pilot valve part 2 having a valve spool 2a by means of a reduction gear 4 provided between one end portion of the spool 2a and the shaft la of the electric pulse motor part 1.

The rotary type four way pilot valve part 2 is also coupled to an axial piston type hydraulic motor part 3 by means of a feedback screw-nut coupling 5, coupling one end portion of the spool 2a to the output shaft 3d of the hydraulic motor part.

An oil supply line 6 introduces hydraulic fluid into a hydraulic motor part 3 from a hydraulic power source (not shown) via a fluid supply port 6a and the rotary type pilot valve part 2. Reference numeral 7 shows an oil return line through which hydraulic fluid returns to the hydraulic power source via a fluid return port 7a. Reference numeral 8 shows an oil line through which the inner chamber 3a of the hydraulic motor part 3 communicates with the oil return line 7. The return line 7 opens to the chamber 3a at a connecting portion 9.

In accordance with the feature of the present invention, a tubular member 10 is arranged in the chamber 3a so as to be either fixedly connected or threadedly engaged at one end thereof to the above-mentioned connecting portion 9. The tubular member 10 extends along the output shaft 3d and has an oil drain opening 10a at the other end thereof.

In accordance with the above-mentioned interior structure of the electro-hydraulic pulse motor of the present invention, even if the electro-hydraulic pulse motor is used in a vertical position in which the shaft 3d directs upwardly, moving elements of the hydraulic motor part 3 such as the bearing 3c of the swash plate system and reciprocal pistons 3b are completely lubricated, since the hydraulic fluid which has actuated the hydraulic motor part 3, is reserved in the abovementioned chamber 30, until the level of the hydraulic fluid within the chamber 3a reaches the opening 10a of the tubular member 10.

The hydraulic fluid overflowing in the chamber 3a returns via the oil return line 7 through the bore of the tubular member 10 and also the oil line 8.

Various modifications may be effected within the spirit and the scope of the present invention, the arrangement of the tubular member according to the present invention providing the most desirable way when considering the over all manufacture of the electro-hydraulic pulse motor.

What we claim is:

1. An electro-hydraulic pulse motor comprising an electric pulse motor:

a rotary type four way pilot valve having a stationary sleeve and a spool coupled to the electric pulse motor at one end part of the spool, the spool being rotatable and axially movable with respect to the stationary sleeve;

an axial piston type hydraulic motor having an inner chamber, a plurality of pistons operable within the inner chamber and an output shaft;

a tubular member having two ends, said tubular member extending along said output shaft of said hydraulic motor and disposed within said inner chamber of said hydraulic motor, one end of said tubular member being fixed within the bottom portion of said inner chamber and the other end constituting an oil drain opening; and

third oil line means connected between said one end of said tubular member and said return line of said first oil line means. 

1. An electro-hydraulic pulse motor comprising an electric pulse motor: a rotary type four way pilot valve having a stationary sleeve and a spool coupled to the electric pulse motor at one end part of the spool, the spool being rotatable and axially movable with respect to the stationary sleeve; an axial piston type hydraulic motor having an inner chamber, a plurality of pistons operable within the inner chamber and an output shaft; first oil line means including an oil supply line conNected between an oil supply port and said four way pilot valve and an oil return line connected between an oil return port and said four way pilot valve; second oil line means including oil lines connected between said four way pilot valve and said hydraulic motor to supply pressurized oil from said four way pilot valve to said hydraulic motor and to return return oil from said hydraulic motor to said four way pilot valve; a tubular member having two ends, said tubular member extending along said output shaft of said hydraulic motor and disposed within said inner chamber of said hydraulic motor, one end of said tubular member being fixed within the bottom portion of said inner chamber and the other end constituting an oil drain opening; and third oil line means connected between said one end of said tubular member and said return line of said first oil line means. 